In typical commercial reproduction apparatus (electrographic copier/duplicators, printers, or the like), a latent image charge pattern is formed on a uniformly charged charge-retentive or photoconductive member having dielectric characteristics. Pigmented marking particles are attracted to the latent image charge pattern to develop such image on the photoconductive member. A receiver member, such as a sheet of paper, transparency, or other medium, is then brought into contact with the photoconductive member, and an electric field applied to transfer the marking particle developed image to the receiver member from the photoconductive member. The electric field to transfer the marking particle developed image to the receiver member from the photoconductive member is typically applied by spraying the backside of the receiver member with electrically charged ions from a corona charging device or, alternatively, by contacting the backside of the receiver member with an electrically biased transfer member. The electrically biased transfer member may be an electrically biased roller in contact with the receiver member or an electrically biased roller in contact with a transport member, such as a flexible belt, on which the receiver member is carried. Another alternative is to first transfer the marking particle developed image directly to an electrically biased intermediate transfer member in the form of a roller or belt and then from the intermediate transfer member to the receiver member.
After transfer to the receiver member, by any of the above alternatives, the receiver member bearing the transferred image is transported to a fixing device where the image is fixed (fused) to the receiver member by heat and/or pressure to form a permanent reproduction thereon. Typically the fixing device has a nip formed between a pair of rollers, one of which, hereafter referred to as the fuser roller, is heated to a temperature high enough to fuse the marking particle image to the receiver member as the receiver member is passed through the nip with the side bearing the marking particle image in contact with the fuser roller. In order to prevent particles of the marking particle image, or the receiver member bearing the fused marking particle image, from sticking to the fuser roller, release oil is typically applied to the fuser roller. After exiting the fuser roller nip a quantity of the release oil typically remains on the receiver member, especially on the side that contacted the fuser roller.
To print an image on both sides of the receiver member, hereafter referred to as duplex printing, a fused marking particle image is formed on side one of the receiver member by the above process, whereafter the receiver member is returned to the process via a duplex return path. In this duplex return path, the receiver member is turned over so as to have a second marking particle developed image transferred and fused to side two of the receiver member. In duplex printing, when transferring the marking particle developed image to side two of the receiver member, if the electric field for transfer is applied by an electrically biased transfer member as described above, some of the fuser release oil from side one of the receiver member, which is now in contact with the biased transfer member, transfers to the surface of the biased roller. During a long duplex printing run a relatively large amount of fuser release oil can thereby accumulate on the biased transfer member. During times such as cycle-down, non-imaging skip frames, and recovery from receiver jams, the biased transfer member is in direct contact with the photoconductive member. During these times some of the fuser release oil accumulated on the biased transfer member during duplex printing transfers to the photoconductive member and can cause image quality defects during subsequent printing. The intermediate transfer member alternative mentioned above also provides a path for fuser release oil to contaminate the photoconductive member. In this case, during duplex printing, fuser release oil from side one of the receiver members accumulates on the electrically biased transfer member that transfers the marking particle developed image from the intermediate transfer member to the receiver member. Then during times such as cycle-down, non-imaging skip frames, and recovery from receiver jams the biased transfer member is in direct contact with the intermediate transfer member. The oil then transfers to the intermediate transfer member and from the intermediate transfer member to the photoconductive member.